Iffy

The one extension method you never knew you needed it that much:

iffy, if-as-a-method. Use conditions in fluent builder patterns, everywhere.

Three flavours to construct your if-method, using:

1. arguments: .If(condition, then, [else])
2. a builder: .If(condition).Then(action).Else([action])
3. or an expression: .If(condition ? action : action)

if, then

new ServiceCollection()
    .If(IsDevelopment(),  then => then.AddSingleton<...>())
    .BuildServiceProvider()

if, then, else

new ServiceCollection()
    .If(IsDevelopment(),  
        then => then.AddSingleton<...>(), 
        @else => @else.AddSingleton<...>())
    .BuildServiceProvider()

if().then()

new ServiceCollection()
    .If(IsDevelopment())
    .Then(s => s.AddSingleton<...>()) 
    .Else()
    .BuildServiceProvider()

or:

new ServiceCollection()
    .If(IsDevelopment())
    .Then(s => s.AddSingleton<...>()) 
    .Else(_ => _)
    .BuildServiceProvider()

Update: the .Then(action) is from now on still executed even when you omit the .Else([action]). For sure your method chain then stops there.

if().then().else()

new ServiceCollection()
    .If(IsDevelopment())
    .Then(s => s.AddSingleton<...>()) 
    .Else(s => s.AddSingleton<...>())
    .BuildServiceProvider()

if ?:

new ServiceCollection()
    .If(IsDevelopment() 
        ? s => s.AddSingleton<...>()
        : s => s.AddSingleton<...>())
    .BuildServiceProvider()

This one is a bit of a hack since it just accepts and executes whatever expression you provide. But it looks so pretty 🥰.

and with any other builder

new ServiceCollection()
    .AddRebus(configure => configure
        .Transport(t => t.UseAzureServiceBus("", "", new DefaultAzureCredential())
            .AutomaticallyRenewPeekLock()
            .SetDuplicateDetectionHistoryTimeWindow(new TimeSpan(0, 2, 0))
            .If(IsDevelopment()
                ? s => s.SetAutoDeleteOnIdle(TimeSpan.FromMinutes(5))
                : s => s.DoNotCreateQueues()
                    .DoNotCheckQueueConfiguration())
            .If(!IsDevelopment(), then => then
                .DoNotCreateQueues()
                .DoNotCheckQueueConfiguration())
            .If(IsDevelopment(),
                then => then
                    .SetAutoDeleteOnIdle(TimeSpan.FromMinutes(5)),
                @else => @else
                    .DoNotCreateQueues()
                    .DoNotCheckQueueConfiguration())
            .If(IsDevelopment())
            .Then(settings => settings
                .SetAutoDeleteOnIdle(TimeSpan.FromMinutes(5)))
            .Else(settings => settings
                .DoNotCreateQueues()
                .DoNotCheckQueueConfiguration())));

benchmark

BenchmarkDotNet=v0.13.4, OS=macOS 13.1 (22C65) [Darwin 22.2.0]
Apple M1, 1 CPU, 8 logical and 8 physical cores
.NET SDK=6.0.405
  [Host]     : .NET 6.0.13 (6.0.1322.58009), Arm64 RyuJIT AdvSIMD
  Job-DYHKDS : .NET 6.0.13 (6.0.1322.58009), Arm64 RyuJIT AdvSIMD

InvocationCount=1000000  IterationCount=5  LaunchCount=1  
WarmupCount=3  

Method	Mean	Error	StdDev
None	3.713 μs	4.506 μs	1.1703 μs
Normal	3.855 μs	3.679 μs	0.9555 μs
IfThen	4.003 μs	5.244 μs	1.3618 μs
IfThenElse	3.958 μs	4.304 μs	1.1178 μs
If	3.970 μs	4.232 μs	1.0991 μs
Builder	3.751 μs	4.092 μs	1.0628 μs

See for yourselves in Iffy.Benchmark.